Field devices are often applied in automation technology for registering and/or influencing process variables. Examples of such field devices are fill level measuring devices, mass flow measuring devices, pressure- and temperature-measuring devices, etc., which, as sensors, register the corresponding process variables, fill-level, flow, pressure and temperature.
Field devices serving for influencing process variables are called actuators, which e.g., as valves, control the flow of a liquid in a section of pipeline or, as pumps, control the fill-level in a container.
A large number of such field devices are manufactured and sold by the firm, Endress + Hauser.
As a rule, field devices in modern manufacturing plants are connected via fieldbus systems (HART, Profibus, Foundation Fieldbus, etc.), with superordinated units (e.g. control systems or control units). These superordinated units serve, among other things, for process control, process visualizing, process monitoring as well as for start-up of the field devices. Referred to as field devices are, generally, also units, such as e.g. remote I/Os, gateways, and linking devices, which are directly connected to a fieldbus and serve for communication with the superordinated units.
Most often, fieldbus systems are integrated into enterprise networks. Therewith, process data or field-device data can be accessed from different areas of an enterprise.
For worldwide communication, company networks can also be connected with public networks, e.g. the Internet.
Modern field devices often include a standardized fieldbus interface, for communication with an open fieldbus system, and/or a proprietary interface, for manufacturer-specific communication with a service unit. Frequently, the service units are portable computers (laptops, Palm handhelds, etc.), such as are known from consumer-electronics (office- and home-computers).
Some field devices are capable of special-functionalities, which can be enabled with a corresponding hardware-key. Such hardware-keys are also known under the labels, “dongle”, or F-chip, in the case of the firm, Endress + Hauser Flowtec. Such special-functionalities relate, frequently, to flow measuring devices having special functions, such as metering functions for batch-operations, diagnostic functions (predictive maintenance), viscosity measuring functions, density-measuring functions, etc.; examples include the Endress + Hauser products, Promass 83 (viscosity, special density, batching, predictive maintenance options), or Promag 53 (batching or ECC options).
In order to be able to use these functions, the user must obtain the corresponding dongle from the device manufacturer. In the case of a first-time use of a dongle in a field device, the serial number of the field device is transferred into the dongle and stored therein. Therewith, the dongle is, from then on, assigned to such field device, and cannot be used in any other field device, since, during turn-on of the device, there is always a checking of the serial number stored in the dongle. In the case of replacement of boards in the field device, this check procedure must be heeded.
For enabling the special software functionalities, the enabling code stored in the dongle is transmitted into the field device. The control program running in the field device ascertains from the enabling code the corresponding software functionality, which is to be enabled. The F-chip includes a PIC processor, which, among others things, is also responsible for encrypted transmission of the information. The different special functions are encoded bitwise in a bit-pattern (the metering function of a Promass-device receives another bit value than the metering function of a Promag-device). The ordered options are programmed into an F-chip during production. Upon turn-on of the device, the measurement amplifier “asks” the F-chip processor which options have been enabled and enables the corresponding parameters for configuring the options.
The unchangeable association between dongle and field device is frequently unsatisfactory for the plant operator. If the user needs, at a plurality of measuring points, e.g. in the case of start-up of a plant, a particular density functionality, then the user is compelled, in order to be able to use this functionality, to obtain a corresponding dongle for each flow measuring device. For many users, the effort is too expensive, to have to obtain a number of dongles for a quasi one-time use of a special-functionality.
Moreover, it is for the device manufacturer very cumbersome, when in the case of the repair of a field device the mainboard must be replaced, to assure, that the user can continue to use its already obtained dongle in the future. For this, the serial number of the old device must be transferred appropriately to the new mainboard.
Furthermore, it is also cumbersome for customers having a number of devices with dongle with different configurations, to keep replacement devices in inventory. In such case, one device per F-chip type, or one device with all F-chip options, must be stored.
Furthermore, it is very cumbesome, when a customer's dongle is misplaced, to provide an appropriate replacement-dongle.